1. Field of the Invention
The present invention relates to a wick of a flame device and, more particularly, to a wick rolled from a metallic meshed body.
2. Description of the Related Art
Wicks in flame devices are used to maintain the flame scale or to evaporate noncombustible fuel or wax that cannot be ignited by an open flame directly. Conventional wicks are normally made out of braided cotton or fiber glass and liquid fuel or melted wax is drawn up through the wick to reach the flame by capillary action. After ignition, fuel vaporizes and combusts on tip of the wick. Being exposed that to the flame, the tip of the cotton wick will be carbonized and burnt out gradually due to high temperature on the top of the flame. Thus, a wick made of consumable material and exposed to high temperature must be adjusted and trimmed every once in a while to maintain combustion. Moreover, wicks produce a diffusion flame as oxygen reacts with vaporized fuel by diffusion. The flame speed is limited by the rate of diffusion, because there is not sufficient oxygen for the reaction of complete combustion. As a result, diffusion flames produced by a wick tend to produce incomplete combustion and more soot particles than premixed flames when the flame scale is enlarged.
U.S. Patent Publication No. 2012/0202160 shows a candle with a ribbon style wick disposed in a candle body. The wick creates a shape in addition to the shape of the wick material itself. The shape of the wick material prior to shaping for use in the candle is in the form of a roll. A flame of the candle takes on the shape created by the placement of the wick. The wick is made of porous material, so that the wick can draw fuel upward to the flame by capillary action. The capillary flow rate is determined by the pore size and density of the wick material and the fuel. If the pore size and density of the wick material is uniform, the wicking capability on each cross-section that draws fuel is fixed. When the wick is in the form of a thin ribbon, it has fewer pores in cross-section and has weaker capillary flow that results in a smaller flame scale during combustion.
If a larger flame scale is needed, one can increase the thickness of the wick that includes more pores on the same cross-section to induce a larger capillary flow rate. However, increase of the wick thickness may cause some drawbacks. Since the pores inside the wick can also absorb fuel, the percentage of the wick's surface area that fuel contacts air directly is reduced when the wick is thickened. A thick wick decreases the efficiency to evaporate fuel and makes it difficult to be lit when the pores in the wick are oversaturated and accumulated with fuel. When a thick wick is lit, fuel inside the pores away from the wick surface is also heated but cannot evaporate properly. It may cause over-heated fuel to expand suddenly and to splash the fuel droplets out of the wick. The problem may deteriorate when using a larger thick wick and a fuel that has a high flash point with a high viscosity.
More important, the wick uses the heat of the flame itself to vaporize its fuel and diffuse the oxidizer (oxygen) into the flame from the surrounding air. The oxygen combines with the fuel by diffusion, and the flame speed is limited by the rate of diffusion. Also, heat generated by the flame also creates convection to carry the hot combustion products away from the fuel source. Therefore, diffusion flames tend to burn slow and to produce soot particles, because there may not be sufficient oxygen for the reaction of complete combustion. Although soot particles typically produced in a diffusion flame becomes incandescent from the heat of the flame and causes the flame to be bright orange-yellow color, incomplete combustion not only produces soot particles but also toxic fumes. It is harmful and even dangerous to users when the flame scale is increased for incomplete combustion. Furthermore, a user has to attend and adjust the wick constantly to control the flame scale, because the wick can burn out due to a high flame temperature. Flame scale varies as the height of the wick relative to fuel changes during combustion. It is thus inconvenient for a user to maintain a stable flame.
The present invention is, therefore, intended to obviate or minimize the problems encountered in the prior art.